AVG Internet Security
AVG Internet Security Firewall blocks the network traffic from external Voip adapters/phones.
Because of this the call recording is not possible untill AVG Firewall is disabled.
MiaRec just doesn't see the network traffic, which is sent by Voip adapter/phone.
Unfortunately, this firewall has very basic configuration options* and there is no way to use it together with MiaRec.
* - this information is valid for AVG v.9.0.730 released on 1st of March 2010.
If you need to record calls, disable it or choose another firewall application.
Below screenshot shows how to disable AVG firewall.